Method of preparing oxidized cellulose gauze



F@b., 7, 1950 w. o. KENYON ET AL. 2,496,797

METHQD 0F PREPARING OXIDIZED CELLULOSFJGAUZE Filed July 26, 1946 0/1577LLEO 4 0 K WILL/AM axe/Wm .32 cam was c. MYRUH MAL/AM I? FOWLER JR.

INVENTORS Patented Feb. 7, 1950 METHOD OF PREPARING OXIDIZED CELLULOSE GAUZE I William 0. Kenyon, Cornelius C. Unruh, and W1!- liam F. Fowler, Jr., Rochester, N. Y, assignors to Eastman Kodak Company, Rochester, N Y., a corporation of New Jersey Application July 26, 1946, Serial No. 686,400 1 Claim. (01. 3 149.2)

This invention relates to a method of preparing a polyanhydrouronic acid from cellulose gauze in pad form and to polyanhydrouronic acid surgical pads.

Previously cotton as such has been treated with gaseous N02 to form an alkali-soluble polyanhydroglucuronic acid. This material has been found to .be useful for surgical purposes and in order to adapt the material for those purposes, it has been necessary to spin the oxidized cellulose and form gauze therefrom. We have found, however, that material for surgical purposes is much more conveniently prepared by taking ordinary surgical gauze, forming a pad therefrom, and treating the so-formed gauze pad with gaseous N02, thereby forming a pad having a substantial polyanhydrouronic acid content. We have found that this material is conveniently cut up into pads of a size useful for surgical purposes with a minimum of handling. We have found that by this method the gauze is uniformly oxidized providing dripping of any liquid N02 or HNOs upon the gauze pad is prevented. We have also found that the gauze may be freed of nitrogen compounds without any deterioration thereof if the gauze is quickly contacted with a large excess of water in the washing operation. We have also found that by using oxidized cellulose, such as scraps thereof, for treating water which is to be employed for the washing of oxidized gauze cations may be removed from the water and the gauze which results from the washing operation with water sotreated is substantially free from any mineral matter which might otherwise be added in the gauze in pad form. Another object of our inven- I tion is to provide a process for oxidizing cellulose gauze with N02 in which a product of uniform shrinkage and carboxyl is obtained by avoiding any dripping of liquid oxidizing or nitrating material upon the cellulose gauze while in pad form. Another object of our invention is to provide a method of washing the cellulose gauze in which no deterioration of the gauze occurs. A still further object of our invention is to remove the cations from water having a mineral content by treating the water with oxidized cellulose, thereby obtaining a water free of cations, which water is useful for washing the gauze prepared in accordance with our process or for any other purpose I lulose gauze in pad form to the action of N02 in gaseous form in a closed system for a time sufficient to impart the desired carboxyl content to the cellulose gauze. In this way a pad of polyanhydroglucuronic acid is prepared.

Our invention may best be explained by reference to the drawings illustrating apparatus in which that process may be embodied. Figure 1 is a vertical section of a device by which cellulose gauze may be formed into a pad for treatment by oxidizing gas. Figure 2 is a washing apparatus in vertical section, adapted for the rapid washing of the oxidized cellulose gauze contaminated with nitric acid and adsorbed oxides of nitrogen so as to prevent heat formation. Figure 3 is a plan .view of apparatus employed to oxidize cellulose gauze while in-pad form by treating the gauze and the oxidizing gas is circulated through and among the layers of cellulose by means of a fan.

In preparing a polyanhydrouronic acid in accordance with our invention cellulose gauze is first formed into a pad. Figure 1 illustrates a.

mechanism by which a pad of the gauze may be formed. That apparatus consists of a perforated drum I having open spaces at the ends whereby gases may circulate through and permeate the gauze pad 'whichis prepared thereon. This drum is contacted with an idle roll 2 so that when the gauze is wound upon the drum, it is smoothed down into uniform layers. Guide rolls 3 are provided to prevent uneven feed of the gauze from the roll of gauze 4 from which it is supplied to the revolving drum. After the gauze is loosely wound upon the perforated roll to form a pad of any desired thickness, the roll I is inserted in a tank or chamber where it is centered by means of .a stainless steel rod 23 terminating in center- I 1 ing arms at each end. Although the invention is I illustrated using two rolls of medium width, it is to be understood that a wide drum and a pad of corresponding width may be used to occupy the length of the oxidizing chamber. Instead, if desired, a plurality of narrow units may be used, the best conditions for operation in any one case being adjusted to the width of gauze which is 1 available- The oxidizing chamber is provided with covers 24 and 25 whereby the rolls are inserted and the chamber is then enclosed so as to be substantially gas tight. In putting the covers 24, and 25 on the chamber, it is desirable that a gasket or some other means be employed to seal the chamber. The chamber is also provided with aninlet 2| and anoutlet 22, each of which is providedwith valves so that after; the desired conditions are obtained within the chamber, it may be closed off. The oxidizing apparatus may also be provided with rolls 2! rotating upon axisv 26 by a rotating mechanism, such as 23 to slowly, 5, rotate the tank while in a horlzontal position If desired, the gauze may be oxidized in'a stationary oxidizing chamber in' 'which afarr is depended upon for circulating;th"'gaseous "NO:

vided with a stainless steel rod 33 for centering the rolls therein, rod 33 terminating, inucenteringi arms at each end, covers 34 and 35 for access to, the chamber, inlet 32 and outlet 3| andafan 36 for circulating the gaseous N02 therein. Also, theinside Walls of thetank should be smoothso that there are no points therein" which would serve as'a nucleus for 'drippingbfiliqu'id." If any one desired to employ a tankof largerdia'meter, the rate' of rotation thereof would necess'arily'be such that the rate'of speed of'revolu'tionpfthe tank would not be toorapidi We have found thatit'is important that the cellulose gauze (once *washin'g is commenced)' after oxidation, be rapidly treated with'an excess of water so as to removethe nitric acidadsorbed by thegauze quickly and to dissipate any heat attendant upon solution of the nitric 'acid'by the" water and the reaction of the 'oxidesof nitrogen therewith. A convenient'wa'shing' apparatus for accomplishing this'pur'po'seis illustrated'in Fig ure 2 where theperforated drum containing a layerof gauze whichhas been oxidized is slowly": unwound, the gauzebeing' unwound'by means of a= partially submerged perforated "drum "I2"'di-" rected towards which'is' a1 spray pip'e l3 which constantly sprays'water onto the gauze as lit is wound by the drum l2, which drum rotates Water withinlwash tank 'I I Wash tank I'Hsj'also provided 'with a" drain" ccnte'ininge "v lve HI whereby used water may be d'raihd from thetanlg' and fresh supplies'of w V n'i'a'y be added; "'Al's'o, itis desirabl'e'durihgthwashihg'operatiqq that T the influx of" water "through" pip el3 "sho uld be j compensated for by drainir'ig o'ffof water analcorresponding rate rmm thetarik I'l. "It is d sirable in" the washing operation that either di tilled waterpr wat'er"which' has beeii rehdered free of cations, such asT537]itieatmenfwith'fsoiap'f oxidized celliiloseJbeh'sd. '50 The' preparation"ofpads of oxidized cellulose N gauze may be "prepar'ed by "winning 'the' gauze upona perforated drum or s'omeotheropen struc ture core"so"'as' warm-a pa'd 'of su'ihcient thick ness to 'give a homogeneous 'produ'ctand awortn: 55 while amount of 'oid'diz'd' gai'i z'e" but not so thick" that thepenetration'of the game by trie'gas mn N02 is difilcult; "After the auz'epad been formed, the roll "or other unit is'place'd in achaniber andcenteredso' thatit' is curarccntact'witu I thesides' of the vessels. Itistheridesii'able'toevae ua'te the tank and'draw'liquidNOz theriri sothat" the liquid N 02 remains'atxthe bottom'o'f theta'nli and out of contactwithltlie gauzef-"Theivesselji I then sealed shut; The clearance bet'wee'ri the gauzefcs Pad and the-liquid .Noz 'sh'ou'l'd"bfsufiofeht that" there will. be no "da'nge'i hfcoiitact' OFI'idLiidNQYT with'the gauze at the speeds at w'hichthe oxidi'z f ingchamberis rotated." The cylindrical 'tahk which the gauze pad was placed'inhori'zontal'po "70 siticn is then rotatedpfor a 'sufficienttiine to b-' tain the desired carboxyl content. on the gauze. In 'the oxidi lngpliocedure the tank should bei'o tated very slowly, suchas tolOiR. PwMflfo'r a. 4 as havin a iameter: of. 1-5. to .20 inches." om- 75 narily the oxidized gauze is'soluble'in dilute alkali when it'hasa carboxyl content imparted thereto of 12% or more. This carboxyl content is im- Y parted by running the oxidizing apparatus for 7-16 hours or more. It is to be understood that variation occurs depending upon the amounts of liquid N02 which are used. Also, temperature variation may change the time required although desirable to carry out the oxidation at or through the gauze. This chamber maybe prof-'1' I. c ose. o'room't mperatu 0-, l u a w degrees variation in temperature is to be tolerated. It a lower, carboxyl content is desired, such as 5,

8, or the oxidizing time is reduced to give the desired carboxyl under the conditions employed.

When the oxidizing process is run for several hours, such as"? or more (varying somewhat with conditions), a positive pressure builds up Within the tank, apparently due to the formation of NO therein which increases the pressure. After the oxidation has been completed; the rotation of the tank' may be stopped'and the pressure may be re leased by opening the valve (valve 2| or 22 After the pressure is released by opening the valve. the chamber may be opened and the drums con taining' the gauze pad may be removedtherefrom. It is' preferred upon removal of the oxidized cellulose roll from the oxidizing chamber to allow the roll to stand orto subject it to an air blast, either of which removes a substantial proportion of the N02 from the roll. This procedure makes, the rclleasier'to handle and contributes to the convenienc'e'of operation. The gauze is then run intoa large excess of mineral-free water rapidly to remove the bulk of th'e'HNOs therefrom without any heating occurring using the apparatus, of. Figure 2. describedabove." After this initial washing, the cellulose 'gau'ze is number of washes with ininera m H l-free water. By passing the gauze into the p esenceof a large excess of water as accomplished by the current of water fiowi'n'gupon thenew layer of gauze and immedia'tel'y' imm'ersing' the same, any deteriora non of the cellulose gauze is avoided.

Ihstead of carrying out the tating'chamber a stationary chambermay be employedftheiliciuid'NOz may be introduced therein, the chamber preferably being' in'vertical position, and a fan may be positioned the 'ga'seous'NOz in the chamber. circulation of the gaseous NQz through the cellulose gauze may be readily obtained. It is desirable that the clearance between the liquidNQz and 'the gauze in a l5inch"diameter tankwhenf run 'asa closed system be at least 2 inches and preferably about 3 i'nche's.

vention i Eatentz'a jle l loq feet of -inch width cellulose..- gauze were loosely wound on a 4-inch perforated rollan'd the ends of the gauze were sewed 011,501 that they remained fixed. The

a weight of %of 'a 'poundh A second rollof this same typ was prepared Thesetwo rolls which had a d ameter at this point of about 7 inches,

were placedi'n a tank tank'was" evacuated to'about mmQ Of mercury" preferably given a oxidation in a r0-,

thereinto. circulate In this way...

For practical con-Q venience it is desirable that this clearance be, no more than 5 inches as otherwise thelcapacity' of understood that j various conditions f H r r H A v gauze formed-a pad upon the roll about 1 inches "thick and had.

H g A of 15-inch diameter and? centered upon a stainless steel rod therein. 4 The and 1500 g. (3.3 pounds) of liquid N02 were drawn into the tank. Care was exercised throughout that none of the liquid N02 or any liquid HNOc which may be present touched the gauze. The tank was thensealed and carefully laid horizontally on rollers which rotated at a speed of 8 R. P. M. and the tank was rotated for 16 hours at room temperature. It was found that a positive pressure of about 10 pounds had built up within the tank. This pressure was released by opening the valve with suitable ventilation in the inlet of the tank. The rolls were removed and allowed to stand briefly in the air so as to evaporate off some of the nitrogen oxides present. The gauze was then unwound from the roll upon which it had been padded and was run in single layers onto a water immersed drum during which operation a spray of mineral-free water played upon the gauze. After the gauze had been wound upon a second drum, it was washed by three washes of water in a period of about 10 minutes. The gauze was then washed in thirty changes of de-mineralized water. A current of warm air (40-50" C.) was used for drying the gauze, the latter being passed as a single layer over wooden rolls in contact with the current of warm air which was circulated around the gauze. An oxidized cellulose gauze was obtained which was completely soluble in 1% sodium hydroxide solution.

Example 2.--Two rolls of cellulose gauze were formed consisting of 50 laps each.. The gauze was introduced and centered in the oxidizing chamber which was then evacuated to mm. and 1250 g. of N02 were added. The tank was then sealed. The fan within the chamber was rotated. The oxidation process was run eighteen hours at room temperature. Pressure was released from inside the vessel and the rolls were then removed, aerated, and the gauze washed and dried as described in the preceding example. To obtain a pad having a substantial content of anhydro-D- glucuronic acid units, the gauze may be fed directly from a roll upon which it is found, or it may be rolled upon a fresh roll as it comes from the drier. For surgical purposes the large pads may be cut into smaller size.

The water which is employed for the washing operation may be distilled water. However, the use of distilled water is unnecessary if the water has been treated so as to remove cations therefrom. For instance, the water employed may be obtained by passing ordinary water through a permutite treatment so that it first has approximately 2-7 P. P. M. of sodium chloride therein. This water is then passed through scrap pieces of oxidized cellulose thereby removing sodium ion from the water. In this form the water is useful for washing the oxidized cellulose gauze. This water may also be employed for any purpose where the absence of cations is desirable and where the presence of a very minute amount of acid is not objectionable. Not only is this treatment valuable for removing alkali metal ions but also water which has been rendered hard due to solution of calcium or magnesium salts may be treated directly with oxidized cellulose or other polyanhydrouronic acids to remove the calcium or magnesium ions therefrom. This is illustrated by preparing a solution of calcium carbonate in distilling water, such as by forming an aqueous solution of calcium carbonate having a concentration of 0.0622 g. per liter of calcium carbonate. By filtering this solution slowly through a pad of oxidized cellulose which had been washed thoroughly with distilled water, which oxidized cellulose had a carboxyl content of 17-18%, a water is obtained which is completely colorless and has an acid reaction toward methyl orange. A solution of magnesium carbonate in water was formed and upon using the same procedure a colorless, clear filtrate is obtained, acidic in its action toward methyl orange indicator. This property of removing cations from water is characteristic of oxidized cellulose or polyanhydrouronio acids generally, those having a higher carboxyl content being the more effective, per unit weight.

Pads of polyanhydrouronic acid have been found to be eminently suitable for surgical purposes, particularly for the prevention of internal hemorrhage. For instance, in a case of a flow of blood internally the pad, preferably in sterilized condition, is placed against the bleeding surface with the use of enough pressure to prevent the further bleeding at that particular point. The polyanhydrouronic acid pads have the property of dissolving or disintegrating within the body within a short time, which is a matter of days, so that there is no need for removal of the pad which has been used for hemostatic purposes internally, even though the incision of the patient has been closed. It is desirable that these pads have a carboxyl content of at least 12% for the most effective use for hemostatic purposes. Nevertheless, our invention includes pads of polyanhydrouronic acids generally. For instance, pads of NOz-oxidized starch or alginic acid may be used for hemostatic purposes, it being desirable that the materials employed be highly refined for surgical uses.

We claim:

A method for preparing oxidized cellulose gauze which comprises forming a pad of the cellulose gauze on a perforated drum, centering the drum containing the gauze pad in a cylindrical chamber, introducing liouid N02 into the chamber so as to not contact the cellulose gauze pad. sealing the chamber and circulating vapors of the N02 therein, whereby only the vapors of the N02 contact the gauze until the cellulose has been oxidized to a substantial degree. sousing the oxidized gauze in water free of cations and after thorough washing, drying the gauze while wound several layers deep upon the drum.

WILLIAM 0. KENYON. CORNELIUS C. UNRUH. WILLIAM F. FOWLER, J R.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,018,650 Debourg Feb. 27, 1912 2,137,169 Levey Nov. 15, 1938 2,232,990 Yackel et a1 Feb. 25, 1941 2,404,367 Durant et a1 July 23, 1946 2,423,707 Kenyon et a] July 8, 1947 

